Toolchain for Java documentation in Oracle Help Center, JDK 11 and later?

User_VLQNU

This is not a question about Java itself, but about the Java documentation in Oracle Help Center.

I like the look'n'feel of the Java documentation HTML-format "books" in Oracle Help Center from JDK 11 onwards. For example, the Javadoc Guide (this "Ask a Question" form tells me that I have to be around for a little while longer before I can post links, hence the following cited URL):

https://docs.oracle.com/en/java/javase/15/javadoc/javadoc.html

I'm curious about the toolchain used to produce those docs.

From the HTML source:

<meta name="generator" content="DITA Open Toolkit version 1.8.5 (Mode = doc)">
<meta name="plugin" content="SP_docbuilder HTML plugin release 18.2.2">    

So, a backlevel (by several years) DITA OT is in the mix, which tells me that the documentation source is DITA. Unsurprising: DITA-based toolchains typically use DITA OT as the starting point for transformations.

However, I can't find any useful references on the web to an "SP_docbuilder" plugin.

DITA OT HTML output enhanced by a bespoke plugin developed in-house at Oracle? Or perhaps a commercially, or even freely, available plugin?

I'm also interested in the search functionality. For example, how deleting the Javadoc Guide "contextual lozenge" in the Search bar widens the scope of the search to, apparently, all of Oracle Help Center. While the links from the Oracle Help Center home page appear to launch separate, heterogeneous documentation websites (different UIs, depending on age and subject matter), the search appears to work across those sites.

I understand if some of the information I'm interested in is proprietary Oracle IP and cannot be shared publicly. Still, I'd be interested to learn as much I can about the toolchain here.